Hydrometallurgical treatment of ores



May 17, 1932- u. c. TAINTON HYDROMETALLURGICAL TREATMENT OF ORES Filed Aug.- 20, 1924 LEAcH TANK.

Sow-mm 679mm: TANK.

H CL Sow-nan.

INVENTOR.

. 6' HCL 0 :75?

Patented May 17, 1932 UNITED STATES PATENT-OFFICE URLYN G. TAINTON, F JOEANNESBURG, TRANSVAAL, UNION OF SOUTH AFRICA HYDROMETALLUBGIGAL TREATMENT 0] 03115 Application filed August 20, 1924. Serial No. 133,121.

is used as the solvent.

The figure of the drawing diagrammatically illustrates the case of an oxidized lead ore containing a mixture of lead carbonateand lead sulphate.

are often undesirable.

sodium sulphate:

QNaCl Pb S0, PbCl are present in other forms:

It is well known that an acid chloride solution is a good solvent for lead, silver, zinc, copper, etc., from roasted or oxidized-ores. In the process of dissolving, however, the metals bring intosolution other salts which For instance, when a lead sulphide ore is roasted, the lead is oxidized to sulphate, and when this-roasted ore is leached, say with acid brine, the sulphate radical combines with sodium to give Na SO ZnO 2NaCl H O =ZnCl CuCO 2NaCl CuCl found for their elimination.

+ 2NaOH Nagcoa The formation. of these salts retards the progress of the reaction and, if the process is to be used contmuously, means must be eous chlorine. This gaseous chlorine is t en brought into contact with an bonate, under properconditions of temperap ture, presence of catalyst, etc. The chlorine then combines with the base of carbonate to form avchloride w of oxygen or carbon-dioxide.

oxide or carthis oxide or ithliberation The chloride thus formed may be used directly in the leaching operation to eliminate the undesirable salts above mentioned. I

As an illustration, take the case of a roasted ore containing lead sulphate as above mentioned. On leaching with brine, we have,

PbSO 2NaCl PbCl Na SO4 Electrolyzing this solution-results in the deposition of lead and the evolution of chlorine:

PbCl electrolyzed yields Pb+Cl The .chlorine is then caused to combine with a suitable oxide or carhonate with evolution of oxygen or carbon-dioxide:

r 2CaG12 0 I 208,003 20301 02 This reaction may be expedited by heat and certain catalysts, notably the presence of cobalt and nickel compounds.

The calcium chloride formed in the above reaction may be added to the next leach to prevent the formation of the sodium sulphate formed in the first reaction,

PbSO; CaCl2 NaCl PbCl CaSQ4+NaCl thus giving a cyclic process, since the calcium sulphate is insoluble and is thus removed from solution. 7

Whereacarbonate or oxide ore is to be treated, the chlorine may be made to combine with the h drogen of water, giving hydrochloric aci and oxygen.

This is done by first heating and then rapidly coolin a mixture of steam and gaseous chlori e. A convenient way 1s to ass the mixture first through a hot and then a cold tube of fused silica or similar'material.

The condensed hydrochloric acid ma then be added to the leach to prevent the orma- 00 tion of the sodium carbonate above mentioned. Thus we have,

PbCl electrolyzed yields Pb and C1 2(31 211 ll-1C1 0 2HC1+ PbCO PbCl H O CO thus giving a cyclic process.

In certain cases, the oxides or carbonates in the ore itself may be made to combine with the chlorine to yield oxygen and chlorides. For example'by bringing chlorine into contact with an ore containing zinc oxide at elevated temperature, the following reaction oc- Similar reactions occur with the other metallic oxides at proper temperatures.

In the case of a sulphide ore, the ore may be first roasted to form oxides, and then while still hot brought into contact with the gaseous chlorine thus:

1 Other metals besides zinc, notably silver and copper, may be effectively chloridized in this way.

As a specific example of the mode of application of this invention, the treatment of electrolytic zinc plant residues will be described. .These residues represent the ma-' terial remaining after the roasted zinc concentrates have been leached with sulphuric acid to dissolve the zinc and copper, and contain usually substantial quantities of lead,

silver and copper. Although this lead is oxidized, i. e. present mainly in sulphate form, I find it is of advantage to first heat it to a temperature around above 400 C. preferably with the admixture of a small quantity, say 2% of common salt or other chloride. The eflect of this is to cause the basic ferric sulphate alwa s present in these residues to breakdown li rating sulphuric acid and this acid then reacts with the sodium chloride yieldinq sodium sulphate and hydrochloric acid WhlCll in turn chloridizes t e silver "minerals. Alternatively instead of the addition of salt, a small quantity of chlorine derived from the subsequent elec trolysis ma be led into the chamber in which the ore is ing heated. This chlorine will react with the metallic oxides present (such as zinc oxide) forming chlorides and liberating free oxygen as previously described.

The calcined material is now referably washed with water to remove the "soluble salts formed in the above reactions. After separation of the solution so formed (from which the valuable constituents such as zinc and copper ma be precipitated by any suitable means suc as the addition of lime) the material is mixed with a solution of sodium and calcium chlorides preferably containing a little free acid and dissolved chlorine.

The lead, silver and gold then dissolve in the solution which is separated from the now barren residue by filtration or settlement. The solution may then be precipitated electrolytically preferably by means of the electrolytic cell described in prior patents of the present applicant. In this way the gold, silver and copper and precipitated and gaseous chlorine are set free, part of which may be used to impregnate the barren solution for use in another leaching cycle. The rest of the chlorine may be passed into an emulsion of milk of lime to which a small quantity of crude nickel sulphate is added. The chlorine combines with the calcium forming calcium chloride, and liberatingoxygen and the solution of calcium chloride is then mixed with the precipitated. solution which is returned to the leaching plant to be used in dissolving the values from a fresh batch of ore.

To give a specific description in the case of an oxidized lead ore containin a mixture of lead carbonate and lead sulp ate, reference is made to the diagram flow sheet illustrated on the figure of the drawing. The ore is leached in a tank indicated at 1, and after leaching this solution is conveyed to a storage tank indicated at 2. From there the SOlIItIOIIlS delivered to an electrolytic cell indicated at 3. The lead is here deposited at the cathode and chlorine gas is evolved at an insoluble anode. The discharging chlorine gas may be treated in one of two ways. For example, itmay be delivered to a hot tube 4 where it reacts with steam under suitable reaction conditions to form hydrochloric acid gas and oxygen. Such are delivered to a condenser indicated at 5 where the hydrochloric acid gas is dissolved in the condensing excess steam and the oxy en is permitted to escape, or it may be use as desired. Or, the chlorine gas may be delivered to a suitable reaction vessel 6, such as a hot revolving kiln, where it comes in contact with and reacts with crushed limestone to be converted into calcium chloride,

"the resulting carbon dioxide and oxy en being permitted to escape, or they may used as desired. The calcium chloride so formed is delivered to a tank indicated at 7 where it may be dissolved. Either the hydrochloric acid solution or the calcium chloride solution (or both) formed as described above may be used for leaching a fresh batch.

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. A process for the recovery of metals from oxidized or roasted ores, which consists in leachingsuch material with a chloride solution to form a metallic chloride electrolyzing the solution with an insoluble anode to precipitate the metal and set free the chlorine, causing such chlorine to react with a reagent capable of forming therewith oxygen and a chloride free of sulphate and carbonate, dissolving the thus formed chloride in water to form a leaching solution of sulphate and carbonate, and leaching 'a fresh lot of ore with such solution..

2. A process for the recover of metals from oxidized or roasted ores, w ich consists in leaching such material with a chloride solution to form a metallic chloride, electrolyzing the solution with an insoluble anode to precipitate the metal and set free the chlorine, causing such chlorine to react with a compound of an alkali earth metal capable of forming oxygen and the corresponding alkali earth metal chloride free of sulphate and carbonate, dissolving the thus formedalkali earth metal chloride in water to form a leaching solution free of sulphate and carbonate, and leaching a fresh lot of ore with such solution.

'3. A process for the recover of metals from oxidized or roasted ores, w ich consists in leaching such material with achloride solution to form a metallic chloride, electrolyzing the solution with an insoluble anode to precipitatethe metal and set free chlorine, I

causing such chlorine to react with a compound containing at least calcium and oxygen to form oxygen and calcium chloride free of sulphate and carbonate, dissolving the thus formed calcium chloride in water to form a leaching solution free of sulphate and carbonate, and leaching a fresh lot of ore with such solution.

' URLY'N C. TAINTON. 

